A method and application of preparing heat-resistant and wear-resistant ultra-high molecular weight polyethylene based on injection molding

Abstract

The present invention relates to a method and application for preparing heat-resistant and wear-resistant ultra-high molecular weight polyethylene (UHMWPE) by injection molding. The UHMWPE is heat-resistantly modified using a minimal cross-linking agent and micro-powdered polytetrafluoroethylene wax. The raw materials used in this method are: 100 parts by weight of a total of an UHMWPE resin and a lubricant, 0.001 to 0.09 parts by weight of a minimal cross-linking agent, 0.2-0.8 parts by weight of an antioxidant, and 0-20 parts by weight of micro-powdered polytetrafluoroethylene wax. After uniform mixing, the UHMWPE product is directly prepared by injection molding. The product exhibits significantly improved heat resistance while maintaining high wear resistance.

Description

Technical Field

[0001] The invention belongs to the field of polymer material processing, and particularly relates to a method and application of preparing heat-resistant and wear-resistant ultra-high molecular weight polyethylene based on injection molding. Background Art

[0002] Ultra-high molecular weight polyethylene (UHMWPE) boasts high wear resistance, impact resistance, self-lubrication, corrosion resistance, low-temperature resistance, and non-water absorption. It is widely used in the textile industry, food machinery, and petrochemical industry. For example, sucker rod centralizers used in oilfield production support and stabilize the sucker rod's trajectory to prevent or reduce eccentric wear between the rod and the tubing. UHMWPE sucker rod centralizers manufactured by injection molding replace traditional glass fiber-reinforced and carbon fiber-reinforced nylon centralizers, offering high wear resistance, long service life, and excellent anti-eccentric wear properties. However, the insufficient heat resistance of the UHMWPE resin itself limits the performance of UHMWPE injection molded products in high-temperature environments. Therefore, it is necessary to heat-resistant modify the UHMWPE while maintaining its high wear resistance to increase its operating temperature.

[0003] Chinese patent CN111363227A discloses a method for modifying an ultra-high molecular weight polyethylene (UHMWPE) composition. Kaolin and nano-zinc-rare earth composite oxides (one or more of yttrium, lanthanum, neodymium, europium, or ytterbium) are combined to provide heat resistance to the UHMWPE. A coupling agent and other additives are then added to prepare a sample through an extruder. The results show that the heat distortion temperature of the UHMWPE was increased when 100g of UHMWPE, 13g of nano-zinc-neodymium composite oxide, 8g of kaolin, 5g of lubricant, and 3g of coupling agent (KH-750) were added.

[0004] Chinese patent CN112521674A discloses a method for producing high-temperature resistant ultra-high molecular weight polyethylene composite pipes. The method uses high-density polyethylene (HDPE), nano-silicon carbide (SiC), calcium carbonate (CaCO3), and aluminum oxide (Al2O3) as modified materials, and treats the filler with a titanate coupling agent. After mixing, the pipe is produced by extrusion molding. When the ultra-high molecular weight polyethylene (UHMWPE) content is 60%, the HDPE content is 25%, the nano-SiC content is 2%, the CaCO3 content is 5%, the Al2O3 content is 5%, and the coupling agent content is 0.5%, the Vicat softening temperature of the UHMWPE pipe is increased.

[0005] The aforementioned modification methods are all based on UHMWPE extrusion molding and are not fully suitable for heat-resistant modification of UHMWPE for injection molding. This is due to significant differences between UHMWPE products produced by injection molding and those produced by extrusion molding. During UHMWPE injection molding, the UHMWPE melt ejected from the injection molding machine nozzle transforms into a "jet stream" of powder particles. After injection into the mold, they fuse together under high pressure and cool to form a product with a dense interior and smooth surface. This differs from the molding principle of UHMWPE extrusion molding, where the resin gradually melts and, under the pressure of the die, the melt gradually transforms into a parison. After cooling and shaping, the product is obtained. Therefore, UHMWPE heat-resistant modification methods based on extrusion molding are not fully applicable to UHMWPE injection molding. Furthermore, experiments have found that the addition of inorganic fillers during UHMWPE injection molding often leads to a sharp decrease in the impact strength of the injection molded product (to the point of being unusable) and a difficulty in significantly increasing the heat distortion temperature. This may be related to the inorganic filler particles hindering the fusion of the UHMWPE "jet stream" powder particles. Although some heat-resistant modifications increase the heat deformation temperature of ultra-high molecular weight polyethylene, the added components may seriously damage the wear resistance of ultra-high molecular weight polyethylene, which makes the unilateral heat-resistant modification lose its use value.

[0006] To improve the heat resistance of ultra-high molecular weight polyethylene (UHMWPE), some literature has also adopted the method of cross-linking UHMWPE. The paper "The Effect of Chemical Cross-linking on the Structure and Properties of Ultra-High Molecular Weight Polyethylene" (Hu et al., Plastics, Issue 2, 1989) discloses the use of a pressing and sintering process to study the effect of DCP cross-linker content on the gel fraction (cross-linking degree) and heat deformation temperature of UHMWPE. When the DCP content is 0.25%, the gel fraction of the UHMWPE sample is 75.1%, and the heat deformation temperature increases from 74°C of the pure material to 85°C, an increase of 14.9%. When the DCP content is 2%, the gel fraction of the UHMWPE sample is 89.1%, and the heat deformation temperature increases to 87°C, an increase of 17.6%.

[0007] The paper "Analysis of Crystallization Behavior and Mechanical Properties of Chemically Cross-linked Ultra-High Molecular Weight Polyethylene" (Liu Ying et al., Plastics, Issue 1, 2004) describes the effects of silane and peroxide cross-linking on the heat distortion temperature of ultra-high molecular weight polyethylene (UHMWPE) using a press-sintering process. The gel fraction of the peroxide-cross-linked sample was 97.47%, and its heat distortion temperature dropped from 95°C (of the pure material) to 49°C, a decrease of 48.4%. The gel fraction of the silane-cross-linked sample was 97.02%, and its heat distortion temperature dropped to 76°C, a decrease of 20%.

[0008] The paper "Structure and Properties of Peroxide-crosslinked Ultra-High Molecular Weight Polyethylene" (Liu Qun et al., Engineering Plastics Application, Issue 11, 2018) discloses the preparation of cross-linked ultra-high molecular weight polyethylene sheets by pressing and sintering. The DCP cross-linking agent content is 0.5-2.5%. TG and DTG tests show that the 5% weight loss temperature (T5) and the temperature corresponding to the maximum weight loss rate (T5) when the DCP content is 2% are significantly different from the 5% weight loss temperature (T5) and the temperature corresponding to the maximum weight loss rate (T5) when the DCP content is 2%. max ) are about 5℃ higher than the pure material.

[0009] It has been verified that in previous ultra-high molecular weight polyethylene injection molding experiments, adding a conventional amount of cross-linking agent could not produce dense injection molded products. Analysis shows that this is because the cross-linking reaction of ultra-high molecular weight polyethylene changes the viscoelastic rheological properties of the ultra-high molecular weight polyethylene, exacerbating the "jet flow" phenomenon, making it difficult to achieve high-pressure fusion of the "jet flow" powder particles, and thus no dense products can be obtained.

[0010] The present invention proposes a new method for preparing heat-resistant and wear-resistant ultra-high molecular weight polyethylene based on injection molding through a large number of experiments. Summary of the Invention

[0011] In order to solve the above-mentioned problems existing in the prior art, the present invention provides a method and application for preparing heat-resistant and wear-resistant ultra-high molecular weight polyethylene based on injection molding, which improves the heat resistance of ultra-high molecular weight polyethylene while maintaining its excellent properties such as wear resistance and impact resistance, thereby solving the problem of poor heat resistance of ultra-high molecular weight polyethylene in wear-resistant applications.

[0012] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0013] A method for preparing heat-resistant and wear-resistant ultra-high molecular weight polyethylene based on injection molding. The molding material is composed of: a total of 100 parts by weight of ultra-high molecular weight polyethylene resin and a lubricant, 0.001 to 0.09 parts by weight of a very small amount of a cross-linking agent, 0.2 to 0.8 parts by weight of an antioxidant, and 0 to 20 parts by weight of micro-powdered polytetrafluoroethylene wax. The antioxidant is used to prevent or reduce thermal degradation of the ultra-high molecular weight polyethylene during the injection molding process, and the micro-powdered polytetrafluoroethylene wax is mainly used for its high heat resistance and good fluidity.

[0014] In a preferred embodiment of the present invention, the molecular weight of the ultra-high molecular weight polyethylene resin is 1.5-10.5 million, preferably 2.5-9.5 million.

[0015] In a preferred embodiment of the present invention, the composition of ultra-high molecular weight polyethylene resin and lubricant comprises 85%-95% of ultra-high molecular weight polyethylene resin and 5-15% of lubricant; the function of the lubricant is to improve the material flowability during the injection molding process.

[0016] In a preferred embodiment of the present invention, the crosslinking agent is an organic peroxide crosslinking agent, selected from but not limited to one or more of di-tert-butyl peroxide isopropylbenzene (BIBP), diisopropylbenzene peroxide (DCP), di-tert-butyl peroxide (DTBP), and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane (DBPH); the crosslinking agent is preferably diisopropylbenzene peroxide (DCP) or 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane (DBPH).

[0017] Among them, when the addition amount of micropowder polytetrafluoroethylene wax is 0, that is, polytetrafluoroethylene wax is not added to the components, and the heat resistance of the injection-molded ultra-high molecular weight polyethylene is mainly improved by cross-linking, then the cross-linking agent content should be 0.005-0.09 weight parts, and when DCP cross-linking agent is selected, the cross-linking agent content should be less than 0.02 weight parts, and when DBPH cross-linking agent is selected, the cross-linking agent content should be less than 0.09 weight parts; due to the shearing, plasticizing and mixing effects of the screw, a moderate and efficient cross-linking reaction occurs in the ultra-high molecular weight polyethylene in the barrel, thereby making the injection-molded ultra-high molecular weight polyethylene obtain high heat resistance. When the cross-linking agent content is too high, a porous structure will be generated inside the injection molded product. This is because the excessive cross-linking reaction causes a drastic change in the rheological properties and morphology of the "jet stream" powder particles, making it difficult to achieve dense compression and fusion, resulting in pore defects inside the product. In addition, defects such as roughness, concave deformation appear on the surface of the injection molded product. Accordingly, the heat deformation temperature, Vicat softening temperature, impact strength, tensile strength, flexural strength, and wear resistance all decrease, or even seriously decrease, and the injection molded product loses its performance.

[0018] When the micropowder polytetrafluoroethylene wax addition is greater than 0, namely based on adding the micropowder polytetrafluoroethylene wax to improve the heat resistance of injection moulding ultra-high molecular weight polyethylene, the preferred 10-15 weight portion of micropowder polytetrafluoroethylene wax addition, and the crosslinking agent should be less than 0.005 weight portion, and the micropowder polytetrafluoroethylene wax addition is larger, and the crosslinking agent addition is smaller, and the rheological property that causes to avoid the crosslinking reaction changes and has a negative effect on the interface bonding of polytetrafluoroethylene-filled ultra-high molecular weight polyethylene.Micropowder polytetrafluoroethylene wax has the high heat resistance of polytetrafluoroethylene, has good fluidity again, is conducive to the injection moulding flow under larger polytetrafluoroethylene polymer addition.Along with the raising of the micropowder polytetrafluoroethylene wax addition, the heat resistance of injection moulding ultra-high molecular weight polyethylene improves, but when addition is too high, heat distortion temperature, impact strength performance, tensile strength descend.

[0019] The method for preparing heat-resistant and wear-resistant ultra-high molecular weight polyethylene based on injection molding of the present invention comprises the following steps: in order to maximize the uniform dispersion of a very small amount of cross-linking agent in an ultra-high molecular weight polyethylene matrix resin, the very small amount of cross-linking agent is pre-mixed with a lubricant, an antioxidant and micro-powdered polytetrafluoroethylene wax, the mixture is mixed evenly, and then the mixture is mixed with the ultra-high molecular weight polyethylene. After the mixing is evenly done, the mixture is directly fed into an injection molding machine for high-pressure and high-speed injection molding, and after cooling, a dense and smooth heat-resistant and wear-resistant ultra-high molecular weight polyethylene injection molded product is obtained.

[0020] In addition, the method for preparing heat-resistant and wear-resistant ultrahigh molecular weight polyethylene of the present invention is also suitable for feeding the mixed materials into an extruder for extrusion molding, and obtaining heat-resistant and wear-resistant ultrahigh molecular weight polyethylene extrusion products after cooling and molding.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] Ultra-high molecular weight polyethylene (UHMWPE) was injection molded with minimal crosslinking agent. Gel fraction testing revealed a high degree of crosslinking in the molded product, while SEM testing revealed a dense interior. Physical and mechanical property testing demonstrated improved heat distortion temperature, Vicat softening temperature, tensile strength, and impact strength, while maintaining excellent wear resistance. Unlike methods like press-sintering, which add higher levels of crosslinking agent to promote UHMWPE crosslinking, the present invention incorporates minimal crosslinking agent. Through the shearing, plasticizing, and mixing action of the injection molding screw, a moderate crosslinking reaction is achieved with minimal crosslinking agent. This also avoids the harmful effects of excessive crosslinking that can hinder the fusion of "jet stream" powder particles. The result is a heat-resistant and wear-resistant UHMWPE injection molded product with a smooth surface and a dense interior.

[0023] The invention adds micro-powdered polytetrafluoroethylene wax (correspondingly reduces the content of the cross-linking agent) to further increase the heat deformation temperature of the injection-molded ultra-high molecular weight polyethylene, meet higher operating temperature requirements, and obtain heat-resistant and wear-resistant ultra-high molecular weight polyethylene injection-molded products with a smooth surface and a dense interior.

[0024] During the molding process of the above method, the basic raw materials and additives are all in powder form, which is convenient for uniform stirring and mixing. After uniform mixing, they can be directly injection molded without the need for special granulation modification, drying and other processes. The process flow is simple and the cost is low. In addition, heat-resistant ultra-high molecular weight polyethylene products with natural color can be obtained, thereby expanding the application range of the products. DETAILED DESCRIPTION

[0025] The specific embodiments of the present invention are described below with reference to the examples. However, the following examples are only used to illustrate the present invention in detail and are not intended to limit the scope of the present invention in any way.

[0026] In the present invention, the molecular weight of the ultra-high molecular weight polyethylene resin is 1.5-10.5 million, preferably 2.5-9.5 million.

[0027] The molding material is composed of: the total amount of ultra-high molecular weight polyethylene resin and lubricant is 100 parts by weight (wherein the content of ultra-high molecular weight polyethylene resin is 85%-95%), based on this, a very small content of cross-linking agent is 0.001-0.09 parts by weight, an antioxidant is 0.2-0.8 parts by weight, and a micro-powder polytetrafluoroethylene wax is 0-20 parts by weight.

[0028] The crosslinking agent is an organic peroxide crosslinking agent, preferably DCP and DBPH crosslinking agents.

[0029] To improve the heat resistance of injection-molded ultra-high molecular weight polyethylene through crosslinking without adding micropowdered polytetrafluoroethylene wax (content is 0), the crosslinker content should be 0.005-0.09 parts by weight. Experimental results show that for optimal heat resistance, the crosslinker content should be less than 0.02 parts by weight when using DCP, and less than 0.09 parts by weight when using DBPH.

[0030] The heat resistance of injection molded ultra-high molecular weight polyethylene is improved mainly by adding micro-powder polytetrafluoroethylene wax. The amount of micro-powder polytetrafluoroethylene wax added is preferably 10-15 parts by weight, and the cross-linking agent is preferably less than 0.005 parts by weight. The greater the amount of micro-powder polytetrafluoroethylene wax added, the smaller the amount of cross-linking agent added.

[0031] In order to maximize the uniform dispersion of the extremely small amount of cross-linking agent in the ultra-high molecular weight polyethylene matrix resin to ensure sufficient cross-linking reaction, the extremely small amount of powdered cross-linking agent is first pre-mixed with the lubricant, antioxidant, and micro-powdered polytetrafluoroethylene wax, mixed for 10 to 15 minutes until uniform, and then mixed with the ultra-high molecular weight polyethylene for 15 to 20 minutes until uniform. The mixture is then directly fed into the injection molding machine for high-pressure injection molding. After cooling, a dense, smooth, heat-resistant, and wear-resistant ultra-high molecular weight polyethylene injection molded product is obtained. When the total amount of material is low, resulting in an extremely low cross-linking agent content and difficult to weigh, various additives can be weighed according to the material amount magnified sufficiently. After pre-mixing, a portion of the pre-mixture is calculated proportionally and mixed with the ultra-high molecular weight polyethylene.

[0032] The following is the test method for the performance of injection molded products:

[0033] Heat Deflection Temperature Test and Vicat Softening Temperature

[0034] Heat deformation temperature and Vicat softening temperature are important indicators for measuring the heat resistance of composite materials. Heat deformation temperature and Vicat softening point tester (KXRW-300CL-3, Chengde Taiding Testing Machine Manufacturing Co., Ltd.) were used. Heat deformation temperature tests were conducted on standard injection-molded strips with dimensions of 80 × 10 × 4 mm (length × width × thickness), a bending stress of 0.45 MPa, and a heating rate of 120°C / h, according to GB / T1634-2019. Vicat softening temperature tests were conducted on standard injection-molded strips with dimensions of 10 × 10 × 4 mm (length × width × thickness), according to GB / T1633-2018, using the A50 method.

[0035] Gel rate test

[0036] The gel fraction of cross-linked UHMWPE is measured according to GB / T 18474-2001. First, take 0.5g to 1g of sample, cut a sieve, and weigh its mass (m1). Wrap the sample with the sieve to form a sample package, and weigh its mass (m2). Then, extract the sieve and sample in a xylene solution for 8 hours. Finally, dry the sample in a 140°C drying oven for 3 hours. After cooling, weigh the sample package and record its mass (m3). The gel fraction is calculated as follows:

[0037]

[0038] Where G i —Gel fraction;

[0039] m1—mass of sieve, mg;

[0040] m2—mass of sample package before extraction, mg;

[0041] m3—mass of the sample package after extraction, mg.

[0042] Wear resistance test

[0043] According to the GB / T 3960-2016 standard, the dimensions of the injection molded specimen are length × width × thickness = 30 × 6 × 7 mm. First, weigh the specimen (m1), then measure its density using a densitometer (ρ). Next, place the specimen on a test ring, apply a pressure of 196 N, and rotate the ring at 200 rpm for 2 hours. Afterward, weigh the specimen (m2). Calculate the volumetric wear using the following formula.

[0044]

[0045] Where, V1—volume wear, cm 3 ;

[0046] m1—mass of sample before wear, g:

[0047] m2—mass of the sample after wear, g;

[0048] ρ—sample density.

[0049] Mechanical properties testing

[0050] Tensile tests were performed using a universal testing machine (KXWW series, Chengde Taiding Testing Machine Manufacturing Co., Ltd.). According to GB / T1040.1.2018, the dimensions of the injection molded strips were 150 × 10 × 4 mm (length × width × thickness) and the tensile speed was 10 mm / min.

[0051] Impact testing was performed using a pendulum impact tester (HIT25P, ZWICK, Germany). In accordance with GB / T1043.1-2008, the dimensions of the injection-molded strips were 80 mm (length × width × thickness) × 10 mm (thickness = 4 mm). The strips were notched using a notch-making machine before testing using the pendulum impact tester.

[0052] Example 1

[0053] A 3 million molecular weight ultra-high molecular weight polyethylene (UHMWPE) resin was used as the base resin. The UHMWPE resin was mixed with 100 parts by weight of lubricant (10% lubricant content), 0.01 parts by weight of DCP crosslinker, and 0.4 parts by weight of antioxidant. After uniform mixing as described above, the mixture was fed directly into a 90F2 horizontal UHMWPE injection molding machine. The barrel temperatures for stages 1 through 3 were 210°C, 250°C, and 275°C, respectively, and the nozzle temperature was 270°C. The screw speed was 98 rpm, and the injection pressures for stages 1 through 4 were 125 bar, 115 bar, 105 bar, and 100 bar, respectively. The injection-molded samples exhibited smooth surfaces and dense interiors. The performance test results are shown in Table 1. The gel fraction of the injection-molded UHMWPE was 64.8%, and the heat distortion temperature increased from 81°C (of the pure material) to 99.1°C, a 22.3% increase. High wear resistance was maintained, and tensile strength and impact strength were also improved.

[0054] Example 2

[0055] A 3 million molecular weight ultra-high molecular weight polyethylene (UHMWPE) resin was used as the base resin. The UHMWPE resin was mixed with 100 parts by weight of lubricant (10% lubricant content), 0.07 parts by weight of DBPH crosslinker, and 0.4 parts by weight of antioxidant. After uniform mixing as described above, the mixture was fed directly into a 90F2 horizontal UHMWPE injection molding machine. The barrel temperatures for stages 1 through 3 were 210°C, 250°C, and 275°C, respectively, and the nozzle temperature was 270°C. The screw speed was 98 rpm, and the injection pressures for stages 1 through 4 were 125 bar, 115 bar, 105 bar, and 100 bar, respectively. The injection-molded samples exhibited smooth surfaces and dense interiors. The performance test results are shown in Table 1. The gel fraction of the injection-molded UHMWPE was 77.1%, and the heat distortion temperature increased from 81°C (of the pure material) to 95.4°C, a 17.8% increase. High wear resistance was maintained, and tensile strength and impact strength were also improved.

[0056] Example 3

[0057] A 3 million molecular weight ultra-high molecular weight polyethylene (UHMWPE) resin was used as the base resin. The UHMWPE resin was mixed with 100 parts by weight of lubricant (10% lubricant content), 15 parts of micronized polytetrafluoroethylene wax, and 0.4 parts by weight of antioxidant. After uniform mixing according to the aforementioned method, the mixture was added to a 90F2 horizontal UHMWPE injection molding machine. The barrel temperatures for stages 1 through 3 were 210°C, 260°C, and 280°C, respectively, and the nozzle temperature was 275°C. The screw speed was 98 rpm, and the system displayed injection pressures for stages 1 through 4 of 125 bar, 115 bar, 105 bar, and 100 bar, respectively. The injection molded samples exhibited smooth surfaces and dense interiors. The performance test results are shown in Table 1. The heat distortion temperature of the injection-molded UHMWPE increased from 81°C for the pure material to 104°C, an increase of 28.4%, while maintaining high wear resistance. Tensile strength and impact strength decreased slightly.

[0058] Example 4

[0059] A 3 million molecular weight ultra-high molecular weight polyethylene (UHMWPE) resin was used as the base resin. The UHMWPE resin was mixed with 100 parts by weight of lubricant (10% lubricant content), 0.002 parts by weight of DCP crosslinker, 15 parts of micronized polytetrafluoroethylene wax, and 0.4 parts by weight of antioxidant. After uniform mixing as described above, the mixture was fed directly into a 90F2 horizontal UHMWPE injection molding machine. The barrel temperatures for stages 1 through 3 were 210°C, 260°C, and 280°C, respectively, and the nozzle temperature was 275°C. The screw speed was 98 rpm, and the injection pressures for stages 1 through 4 were 125 bar, 115 bar, 105 bar, and 100 bar, respectively. The injection-molded samples exhibited smooth surfaces and dense interiors. The performance test results are shown in Table 1. The heat distortion temperature of the injection-molded UHMWPE increased by 29.9% from 81°C for the pure material to 105.2°C, while maintaining high wear resistance. Tensile strength and impact strength decreased slightly.

[0060] Comparative Example 1

[0061] A 3 million molecular weight ultra-high molecular weight polyethylene (UHMWPE) resin was used as the base resin. The UHMWPE resin was mixed with 100 parts by weight of lubricant (10% lubricant content), 0.3 parts by weight of DCP crosslinker, and 0.4 parts by weight of antioxidant. After uniform mixing according to the aforementioned method, the mixture was added to a 90F2 horizontal UHMWPE injection molding machine. The machine temperatures for stages 1 through 3 were 210°C, 250°C, and 275°C, respectively; the nozzle temperature was 270°C; and the mold temperature was 70°C. The screw speed was 98 rpm; and the system displayed injection pressures for stages 1 through 4 as 125 bar, 115 bar, 105 bar, and 100 bar, respectively. The performance test results of the injection-molded samples are shown in Table 1. The heat deformation temperature of the injection-molded UHMWPE decreased from 81°C (pure material) to 67°C, a decrease of 17.3%. The tensile strength and impact strength also decreased significantly. SEM observation revealed a significant amount of porosity within the product.

[0062] Comparative Example 2

[0063] A 3 million molecular weight ultra-high molecular weight polyethylene resin was selected as the base resin. The ultra-high molecular weight polyethylene resin was mixed with 100 parts by weight of lubricant (10% lubricant content), 25 parts of micronized polytetrafluoroethylene wax, and 0.4 parts by weight of antioxidant. After uniform mixing according to the aforementioned method, the mixture was added to a 90F2 horizontal ultra-high molecular weight polyethylene injection molding machine. The barrel temperatures for stages 1 through 3 of the injection molding machine were 210°C, 260°C, and 280°C, respectively, and the nozzle temperature was 275°C. The screw speed was 98 rpm, and the system displayed injection pressures for stages 1 through 4 of 125 bar, 115 bar, 105 bar, and 100 bar, respectively. The performance test results of the injection molded samples are shown in Table 1. The heat deformation temperature of the product decreased from 81°C (for the pure material) to 70.4°C, a decrease of 13.1%, with significant reductions in tensile strength and impact strength.

[0064] Comparative Example 3

[0065] A 3 million molecular weight ultra-high molecular weight polyethylene resin was selected as the base resin. The ultra-high molecular weight polyethylene resin was mixed with 100 parts by weight of lubricant (10% lubricant content), 0.01 parts by weight of DCP crosslinker, 15 parts of micro-powdered polytetrafluoroethylene wax, and 0.4 parts by weight of antioxidant. After uniform mixing according to the aforementioned method, the mixture was added to a 90F2 horizontal ultra-high molecular weight polyethylene injection molding machine. The injection molding machine barrel temperatures for stages 1 through 3 were 210°C, 260°C, and 280°C, respectively, and the nozzle temperature was 275°C. The screw speed was 98 rpm. The system displayed injection pressures for stages 1 through 4 of 125 bar, 115 bar, 105 bar, and 100 bar, respectively. The performance test results of the injection molded samples are shown in Table 1. The heat deformation temperature of the product increased from 81°C (for the pure material) to 96.1°C, an increase of 18.6%, which is lower than that of Examples 1, 3, and 4.

[0066] Table 1 Performance test results of modified ultra-high molecular weight polyethylene injection molding samples

[0067]

[0068] As can be seen from the above examples and Table 1, the present invention uses a very small amount of cross-linking agent and fine powder polytetrafluoroethylene wax to modify the injection molded ultra-high molecular weight polyethylene, which significantly improves the heat resistance of the product while maintaining a high wear resistance.

[0069] The above examples are only some embodiments of the present invention, not all embodiments. Those skilled in the art may modify these embodiments based on the above embodiments, and these embodiments are still covered by the claims of the present invention. The present invention covers all reasonably equivalent variations and modifications derived from the above embodiments.

Claims

1. A method for preparing heat-resistant and wear-resistant ultra-high molecular weight polyethylene based on injection molding, characterized in that: The molding material comprises: 100 parts by weight of an ultra-high molecular weight polyethylene resin and a lubricant, 0.001 to 0.09 parts by weight of a very small amount of a cross-linking agent, 0.2 to 0.8 parts by weight of an antioxidant, 10 to 15 parts by weight of a micro-powdered polytetrafluoroethylene wax, and less than 0.005 parts by weight of the cross-linking agent; the greater the amount of micro-powdered polytetrafluoroethylene wax added, the smaller the amount of the cross-linking agent added; and the cross-linking agent is selected from one or more of di-tert-butyl peroxide isopropylbenzene (BIBP), diisopropylbenzene peroxide (DCP), di-tert-butyl peroxide (DTBP), and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane (DBPH).

2. The method according to claim 1, characterized in that The molecular weight of the ultra-high molecular weight polyethylene resin is 1.5-10.5 million.

3. The method according to claim 2, characterized in that The molecular weight of the ultra-high molecular weight polyethylene resin is 2.5-9.5 million.

4. The method according to claim 1, wherein In the composition of ultra-high molecular weight polyethylene resin and lubricant, the content of ultra-high molecular weight polyethylene resin is 85%-95%, and the content of lubricant is 5-15%.

5. The method according to claim 1, wherein The crosslinking agent is dicumyl peroxide (DCP) or 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane (DBPH).

6. The method according to any one of claims 1 to 5, characterized in that The method comprises the following steps: firstly pre-mixing a very small amount of cross-linking agent with a lubricant, an antioxidant and micro-powdered polytetrafluoroethylene wax, mixing the mixture evenly, then mixing the mixture with ultra-high molecular weight polyethylene, directly feeding the mixture into an injection molding machine for high-pressure and high-speed injection molding, and obtaining a dense, smooth, heat-resistant and wear-resistant ultra-high molecular weight polyethylene injection-molded product after cooling.

7. The method according to claim 6 is used in the preparation of heat-resistant and wear-resistant ultra-high molecular weight polyethylene based on injection molding.

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